The present invention relates generally to a reader and/or writer for an IC card as external memory, and more particularly to the device of a type having a casing, a carrier longitudinally movable in the casing but normally kept at a waiting position by spring means near to a slit formed in a front end wall of the casing for receiving the IC card inserted through said slit, and a contact head mounted in the casing near a back end wall so that when the IC card is manually pushed against the force of the spring means the IC card held by the carrier is brought to be electrically connected with the contact head for reading and/or writing.
In the device of the type referred to above, it is necessary to lock the card or the carriage supporting thereof in the position for reading and/or writing operation. For instance, U.S. Pat. Nos. 4,449,775 and 4,575,703 as well as U.S. patent application Ser. No. 55,283 filed on May 29, 1987, now U.S. Pat. No. 4,835,375, the carriage only is locked. In this type of locking, however, it can not be avoided that the card is erroneously displaced on the carriage or taken out of the device during the operation. For instance, U.S. Pat. No. 4,527,052 and U.S. patent application Ser. No. 747,148 filed on June 20, 1985, now U.S. Pat. No. 4,724,310, disclose locking of the IC card held and brought by the carriage in the position for reading and/or writing at the trailing edge thereof. In this type of locking, however, the spring means for normally keeping the carriage in the waiting position and drawing the carriage back to said position from the operating position when the reading and/or writing is over must be considerably strong so that such force may adversely affect on the card usually made of a thermoplastic polymer, above all of less thickness, which may cause erroneous reading and/or writing, or even make it impossible.
Meanwhile, it is necessary to establish good electrical connection between contact points of the IC card which are embedded in the plastic card to be flush with a surface of one side thereof and contact points of or yieldably planted in the contact head of the device in the operating position. For that purpose, it has been proposed to provide a contact head adapted to be relatively movable a little towards the operating position together with the card held by the carriage and concurrently vertically to contact with the card surface so as to cause scrape between the both contact points for automatical cleaning, e.g. by forming a sloped floor for said contact head (see for instance U.S. Pat. No. 4,602,351 and said U.S. patent application Ser. No. 747,148, now U.S. Pat. No. 4,724,310.
In the prior arts, however, force necessary for manually pushing the card and consequently the carriage holding the card is considerably increased by a force urging the contact head against the IC card and varied depending on the thickness thereof. A distance for said automatical cleaning of contact points is also fairly varied depending on the card thickness.